The Streptococci make up a medically important genera of microbes known to cause several types of disease in humans, including, for example, otitis media, conjunctivitis, pneumonia, bacteremia, meningitis, sinusitis, pleural emphysema and endocarditis, and most particularly meningitis, such as for example infection of cerebrospinal fluid. Since its isolation more than 100 years ago, Streptococcus pneumoniae has been one of the more intensively studied microbes. For example, much of our early understanding that DNA is, in fact, the genetic material was predicated on the work of Griffith and of Avery, Macleod and McCarty using this microbe. Despite the vast amount of research with Streptococcus pneumoniae, many questions concerning the virulence of this microbe remain. It is particularly preferred to employ Streptococcal genes and gene products as targets for the development of antibiotics.
The frequency of Streptococcus pneumoniae infections has risen dramatically in the past 20 years. This has been attributed to the emergence of multiply antibiotic resistant strains and an increasing population of people with weakened immune systems. It is no longer uncommon to isolate Streptococcus pneumoniae strains which are resistant to some or all of the standard antibiotics. This has created a demand for both new anti-microbial agents and diagnostic tests for this organism.
Proteins essential for growth of bacterial make excellent candidates for anti-infective agents. GTPases play important physiological roles in both prokaryotic and eukaryotic cells. Regulatory GTPases consist of GTP-binding domains conserved through evolution (H. R. Bourne, et al. Nature 349:117-127 (1991)). Biological activity is controlled by conformational changes which occur when a bound GTP molecule is bound or released by hydrolysis to GDP. In addition to the conserved GTP-binding domains, bacterial GTPases share other conserved protein domains (K. Zuber, et al., Gene 189:31-34 (1997). Era is a GTP-binding protein essential for growth in Escherichia coli (N. Gollop & P. E. March. J. Bacteriol. 173:2265-2270 (1991); H. E. Takiff, et al. J. Bacteriol. 171:2581-90 (1989)), and other Gram-negative bacteria. A homolog in S. mutans, spg, is important for adaptation to environmental stresses (Y. Yamashita et al. J. Bacteriol. 175:6220-6228). Mutations in era proteins cause a loss of cell viability or a decreased ability to respond to stresses that occur when a pathogen invades a host. Inhibitors of era GTPases would interfere with intracellular signalling necessary for normal growth as well as adaptation to environmental changes such as that which occurs when a pathogen invades a host and would therefore be lethal or inhibitory to the bacterium and thereby have utility in anti-bacterial therapy.
Clearly, there is a need for factors, such as the novel compounds of the invention, that have a present benefit of being useful to screen compounds for antibiotic activity. Such factors are also useful to determine their role in pathogenesis of infection, dysfunction and disease. There is also a need for identification and characterization of such factors and their antagonists and agonists which can play a role in preventing, ameliorating or correcting infections, dysfunctions or diseases.
The polypeptides of the invention have amino acid sequence homology to a known era protein (Swiss-Prot Accession Number P37214; GenBank Accession Number L03428).